1. Field of the Invention
The present invention relates generally to dual flush systems for toilets and particularly to a refill device for dual flush systems.
2. Description of Prior Art and Related Information
Demand for dual flush toilets continues to grow as a result of concerns over water shortage. Such toilets conserve water by providing the user with options for a partial flush and full flush for liquid and solid wastes, respectively. Dual flush toilets typically deliver lesser or greater amounts of refill water to the bowl as a result of a partial or full flush, respectively, by varying the time during which refill water is directed to the bowl. Thus, less time is provided for flowing refill water to the bowl during a partial flush while more time is provided for a full flush.
In many European countries, a “wash-down” toilet bowl 2 as shown in FIG. 1 is typically employed whereby the force of the water head during a flush pushes the contents in the bowl 2 through a relatively large drain pipe. In such wash-down toilets, only a relatively minor amount of fluid is required to reside in the bowl 2 in a default, rest state so as to block sewage gas from the drain pipe 4 from entering through the bowl into the surrounding atmosphere.
In several non-European countries, such as the U.S., a siphonic toilet is employed. FIG. 2 is a cutaway side view of a typical siphonic toilet 5 as used in the U.S. An inverted U-shaped flow path 7 is disposed between a toilet bowl 9 and an outlet 12, such as a drain pipe. Siphonic toilets 5 require sufficient water in the bowl 9 to fill the inverted flow path so as to induce siphonic action that drains waste in the bowl 9 during a flush cycle. As shown in FIG. 3, siphonic toilets 5 typically leave a very small amount of water 14 in the bowl 9 after a flush cycle. This residual water 14 is insufficient for blocking sewage gas from the outlet 12 and for preparing the bowl 9 for the next flush. Accordingly, the bowls 9 in siphonic toilets 5 need to be refilled with fresh water to a certain level in order to function properly.
The problem with incorporating a dual flush system into a siphonic toilet lies in refilling the bowl to a proper level without wasting water. In a dual flush system, the amount of time provided for refilling the bowl varies with each type of flush. In particular, more time is provided for refilling during a full flush, and less time for a partial flush. Accordingly, if the same volume of refill water is supplied for both types of flushes, then problems arise with either oversupply or undersupply of water due to the differing refill times for partial and full flushes. For example, oversupply occurs when a toilet is set to provide a high flow rate of refill water for a partial flush. Though adequate for the partial flush which has a shorter duration of time for refill, excessive refill water is directed into the bowl and thus wasted during the longer, full flush. Conversely, if a lower flow rate of refill water is delivered for each type of flush, then the bowl will be adequately filled during the longer, full flush. During the partial flush, however, the bowl will be inadequately filled due to the shorter refill time.
Thus, the varying durations of time for refilling the bowl in a dual flush siphonic toilet leads to either water waste or insufficient refilling of the bowl.